convert/gnuarch: add cat-log payload to commit description

bisect: improve hg bisect -c (relative paths, error handling) hg bisect -c failed with a relative path or when the executable wasn't found. Use util.find_exe()+os.spawnl() instead of os.spawnlp() and improve the handling of errors (killed process, exe not found). Thanks to Georg Brandl for reporting it.

merge with crew-stable

convert/gnuarch: correct indentation

merge with crew

test-audit-path: add one more test (issue 1450)

convert/gnuarch: follow continuation-of revisions Built on top of previous patches: - continuation-of parsing - registered archives retrieval - use of fully qualified revisions This allows the converter scanning for more source revisions following the tree versions 'leaked' through the continuation-of informations. Coupled with the registered archives retrieval, this makes possible to decide to follow such a hint or stop scanning for more revisions. This also implies some changes in the retrieval of some base-0 revisions when they're continuation-of other revisions, in that case a 'replay' will work where a simple 'get' fails because the dir exists already. I found the code dealing with 'replay' quite good as it has already a fallback to 'get' in the error path.

convert/gnuarch: retrieve known archive names list This will make possible in a followup patch to prevent following history that is not reachable because an archive is unknown to the user.

convert/gnuarch: parse continuation-of revisions in gnuarch source In GNU Arch, continuation-of was often used for: - tagging revisions - continue working on a project in a new archive, because arch was scaling poorly in revision numbers (cat-logs were slow to be parsed and scanned through) - very similar to the previous point, fork his own branch of a project. Parsing this header information will allow to 'follow' new history because it often hints at older/forked/personal revision trees. This patch however just implements the parsing of the continuation-of header. A followup patch will implement the proper use of this new information.

convert/gnuarch: use fully qualified revisions There is no need loosing information in the conversion process. This could lead to wrong shamap mappings if different archives used the same 'version' naming.